Year 9 > Physics > Flashcards

Physics Flashcards

(72 cards)

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1
Q

Force
(Definition)

A

A push or pull on an object caused by it interacting with another object.

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2
Q

What does Force affect?

A
  • Changes speed
  • Changes direction
  • Changes shape
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3
Q

Two types of Force

A

1) Contact Force
2) Non-contact Force

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4
Q

Examples of Contact Forces

A

Thrust
Drag / Air Resistance
Upthrust
Compression
Tension
Normal Contact Force / Reaction Force

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5
Q

Examples of Non-contact Forces

A

Weight
Electrostatic force
Magnetic force

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6
Q

Free-Body Diagram
(Definition)

A

A diagram that only shows only the object (not the surroundings) and the individual forces acting upon it

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7
Q

Rules of Free-Body Diagrams

A

1) The larger the force, the longer the force arrow.
Ideally, the length of the arrow should be proportional to he magnitude (size of the force).
2) Force arrows always start touching the object and point away from it.
3) The start of the force arrow should be where the force acts
E.g. Weight acts from the centre of mass. Friction acts from where the objects are in contact.
4) Force arrows should be labelled
E.g. Weight / tension / etc.

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8
Q

Resultant Force
(Definition)

A

The single force that would have the same effect as all the separate forces acting on an object.
It is the total sum of all the forces.

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9
Q

What happens when the resultant force is ZERO?

A

The object can either be STAITIONARY or moving at CONSTANT SPEED
* When an object is moving at a constant speed, there will be resistive forces, neutralising the resultant force to 0
* When an object is stationary there will be no resistive forces

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10
Q

What happens when there IS a resultant forces acting on an object?

A

The object will accelerate

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11
Q

Mass

A

The amount of matter an object is made of (kg)

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12
Q

Weight

A

The force acting on an object due to gravity (N)

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13
Q

How to calculate weight

A

Weight = mass x gravitational field strength

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14
Q

How to tell a quantity is DIRECTLY PROPORTIONAL

A

1) It’s results are in a straight line
2) It’s results passes through the origin

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15
Q

How to tell a quantity follows Hooke’s Law

A

The extension of the object is DIRECTLY PROPORTIONAL to the FORCE APPLIED

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16
Q

How to calculate force

A

Force (N) = spring constant (N/m) x extension (m)
F = ke

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17
Q

What will prove Hooke’s Law does not always work?

A

1) Any objects beyond the Limit of Proportionality
2) Elastic bands - as they do not go back to their original length after time

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18
Q

What will adding weight beyond the limit of proportionality do?

A

It will produce large extensions as the spring will become PERMANENTLY DEFORMED and not return to its original shape

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19
Q

What happens to an ELASTICALLY DEFORMED object?

A

It goes back to its original shape and length when the force is removed

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20
Q

What happens to an INELASTICALLY DEFORMED object?

A

It does not return to its original shape and length once the force is removed

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21
Q

The 8 Energy Stores

A

Chemical
Kinetic
Gravitational Potential
Elastic Potential
Thermal
Nuclear
Electrostatic
Magnetic

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22
Q

The 4 Energy Pathways

A

Electrical
Mechanical
Heating
Radiation

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23
Q

How to calculate power

A

Power = energy transferred / time
= work done / time

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24
Q

How many watts are there in a kilowatt?

A

1000

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25
What is power measured in?
Watts / Kilowatts
26
What happens when a force makes things CHANGE?
The force mechanically transfers energy between energy stores E.g Friction transfers energy mechanically into the thermal store
27
How to calculate the work done?
Work = force x distance moved in direction of force W = FS Work done = energy transferred between stores
28
What is the unit of work?
Newton metre (Nm) OR Joule (J)
29
What is WORK DONE?
ENERGY TRANSFERRED
30
Power
The rate of energy transfer. How much energy is transferred per second.
31
How to calculate power
Power (W) = energy transferred (J) /time (s) = E/t
32
How many Watts in 1Joule/sec
1W = 1J/s
33
Dissipated Energy
Energy can be transferred into a useful energy store/an unwanted energy store. We say the energy has been DISSIPATED (wasted). Most often, the energy dissipated is transferred to the thermal stores of the surroundings.
34
Efficiency
Measures what proportion of the energy is transferred to the useful store. (E.g. a torch transfers energy to light - the radiation pathway - and to the thermal stores of the torch and its surroundings. The light is the useful energy.) Efficiency is usually given as a percentage.
35
How to calculate Efficiency
Efficiency (%) = Useful energy output / Total energy input x 100 Efficiency (%) = Useful power output / Total power input x 100
36
How to calculate the energy transferred to the gravitational potential store
Change in gravitational potential energy = mass x gravitational field strength x change in height E^G = mgh
37
How to calculate the energy transferred to the kinetic store
Energy in the kinetic store ( J ) = mass ( kg ) x speed^2 ( ms^-1) / 2 E^K = mv^2 / 2
38
How to calculate the energy transferred to the elastic store
Energy in the elastic store ( J ) = spring constant ( Nm^-1 )x extension ( m ) / 2
39
Electrical Conductor
A material that allows electrical charge to easily move through it
40
Electrical Insulator
A material that does not allow electrical charge to easily move through it
41
Static Charge
A static charge is an electric charge that cannot move
42
Static Electricity
When certain insulators are rubbed together, and FRICTION causes negatively charged ELECTRONS to move from one object to another. E.g. Cloth and Glass Rod Ex - when rubbing a cloth repeatedly over a glass rod, the electrons from the cloth will transfer to the glass rod, making the cloth become more positive charged (with more protons than electrons), and the glass rod more negatively charged (with more electrons than protons).
43
Electric Field
A region where a force acts on a charge particle - it is created around any electrically charged object. It is represented by FIELD LINES
44
Field Lines - RULES
* Always drawn at right angles to a charged object's surface * Direction of lines shows which way the force acts on a positive charge
45
Current (Factfile)
* Current is the rate of flow of charge around a complete circuit, from the positive terminal to the negative terminal * Current is measured in Amps (A) with an ammeter placed in the flow of current, i.e. the circuit * As the unit of charge (in Physics) is the coulomb (C), a current of 5.0A would mean that 5 coulombs of charge will pass through a component every second
46
The Law of Conservation of Energy
* The sum of all current entering a junction = The sum of all current leaving a junction * Charge, like energy, is conserved. Charge cannot be created or destroyed. * At any junction where a circuit divides into two or more separate pathways, they will always combine back together
47
Potential Difference (Factfile)
* Potential difference measures the work done per unit unit charge. It is also a measure of "push". * Potential difference is measured in volts ( V ) * One volt is equivalent to one Joule transferred by 1 coulomb of charge (1V = 1J/C) * It is measured with a voltmeter connected in parallel
48
Resistance (Factfile)
* Resistance is a measure of how easily current can flow in a circuit. It is the ratio of potential difference to current (* Increasing the resistance - adding more bulbs, a greater length of wire - decreases the current for a given potential difference (+ vice versa) * Increasing the potential difference for a given resistance will increase the current (+ vice versa)) * The unit of resistance is the Ohm *A resistor is a component designed to have a specific resistance
49
How to calculate Resistance
Resistance = potential difference / current R = V/I
50
What two things will change the current?
1) The resistance 2) The potential difference
51
Scalar (Definition)
Measure of magnitude and NOT direction
52
Vector (Definition)
Measure of magnitude and direction
53
Scalar quantity EXAMPLES
Speed Distance Temperature Mass Density Energy (Time) (Power)
54
Vector quantity EXAMPLES
Displacement Force Acceleration Velocity Weight Momentum
55
Displacement (Definition)
Measured in a straight line, starting from starting point and ending at the ending point E.g. "300m North"
56
Velocity (Definition)
How fast something is moving in a specific direction
57
How to calculate velocity
Velocity (m/s) = distance (m) / time (s) v = s/t
58
How to calculate displacement
Distance (m) = velocity (m/s) x time (s)
59
Acceleration (Definition)
The rate of change of VELOCITY
60
How to calculate acceleration
Acceleration (m/s^2) = change in velocity (m/s) / time taken (s) a = v-u/t
61
Directly proportional (Definition)
They change at the same rate. If one quantity increases, the other increases proportionally, and if one quantity decreases, the other decreases proportionally.
62
How would you determine how far the object has travelled from this velocity-time graph?
Calculate the area under the line. An irregular shape would mean having to count the number of squares - the number of 50%+ full squares x the distance represented by each square (calculating the area of one square)
63
When will you have an object moving at a constant speed but at a constantly changing velocity?
When it is moving in a circular motion
64
The typical speed of a person walking
1.5 m/s
65
The typical speed of a person running
3.0 m/s
66
The typical speed of a person cycling
6.0 m/s
67
The typical speed of a car
25 m/s
68
The typical speed of a train
30 m/s
69
The typical speed of a plane
250 m/s
70
Uniform acceleration (Definition)
Speeding up/Slowing down at a CONSTANT RATE
71
Drawing Distance-Time Graphs (Rules)
1) Gradient = speed (The steeper the graph, the faster it's going) 2) Flat sections = stationary 3) Straight uphill sections = constant speed 4) Steepening Curve = acceleration 5) Levelling-off Curve = deceleration 6) If the object is changing speed, you can find its speed at a point by finding the gradient of the tangent to the curve at that point
72
Drawing Velocity-Time Graphs (Rules)
1) Gradient = acceleration (The steeper the graph, the greater the acceleration or deceleration) 2) Flat sections = constant speed 3) Uphill sections = acceleration 4) Downhill sections = deceleration 5) Curve = changing acceleration 6) The area under any section of the graph (or all of it) is equal to the distance travelled in that time period 7) If the section under the graph is irregular, count the squares under the line and multiply by the value/area of one square
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